The relationship between mosquito abundance and rice field density in the Republic of Korea

Abstract

BackgroundJapanese encephalitis virus (JEV), the causative agent of Japanese encephalitis (JE), is endemic to the Republic of Korea (ROK) where unvaccinated United States (U.S.) military Service members, civilians and family members are stationed. The primary vector of the JEV in the ROK is Culex tritaeniorhynchus. The ecological relationship between Culex spp. and rice fields has been studied extensively; rice fields have been shown to increase the prevalence of Cx. tritaeniorhynchus. This research was conducted to determine if the quantification of rice field land cover surrounding U.S. military installations in the ROK should be used as a parameter in a larger risk model that predicts the abundance of Cx. tritaeniorhynchus populations.Mosquito data from the U.S. Forces Korea (USFK) mosquito surveillance program were used in this project. The average number of female Cx. tritaeniorhynchus collected per trap night for the months of August and September, 2002-2008, was calculated. Rice fields were manually digitized inside 1.5 km buffer zones surrounding U.S. military installations on high-resolution satellite images, and the proportion of rice fields was calculated for each buffer zone.ResultsMosquito data collected from seventeen sample sites were analyzed for an association with the proportion of rice field land cover. Results demonstrated that the linear relationship between the proportion of rice fields and mosquito abundance was statistically significant (R2 = 0.62, r = .79, F = 22.72, p < 0.001).ConclusionsThe analysis presented shows a statistically significant linear relationship between the two parameters, proportion of rice field land cover and log10 of the average number of Cx. tritaeniorhynchus collected per trap night. The findings confirm that agricultural land cover should be included in future studies to develop JE risk prediction models for non-indigenous personnel living at military installations in the ROK.

When Japanese Encephalitis Virus Invaded Eastern Hemisphere – The History of the Spread of Virus Genotypes

“…On the other hand, land use, and in particular irrigated and paddy fields areas, was considered, given the strong relationship existing between rice field density and mosquito populations, especially Cx. tritaeniorhynchus (Richards et al, 2010), and given the role of flooded rice system on JE outbreaks (Akiba et al, 2001;Keiser et al, 2005). Regarding both ecoregions and land use, we determined regions, which were also consistent with those proposed by Solomon et al (2003).…”

Seasonal abundance and potential of Japanese encephalitis virus infection in mosquitoes at the nesting colony of ardeid birds, Thailand

“…Furthermore, the study of Takagi et al also supported rice cultural practices that have the effect on the abundance of mosquitoes in Northern Thailand [19] . At any rate, the number of mosquitoes may also vary depending on several factors such as rice field density, insect predators and artificial control of the water supply to the rice field [20,21] .…”

How environmental conditions impact mosquito ecology and Japanese encephalitis: An eco-epidemiological approach

“…JEV transmission is related to agricultural activities, which involve the transmission cycles of mosquitoes in rice paddies and interaction with human beings in the farmland. It is apparent that rice paddies are the preferred development sites for mosquito vectors, which provide an important transmission site for mosquitoes (Henrich et al, 2003;Impoinvil et al, 2011;Masuoka et al, 2010;Richards et al, 2010).…”